OpenSearch：文檔推送Demo與日誌

程式調試過程中日誌輸出配置

1. pom.xml中加入Java SDK的依賴，如果已經加入，請忽略。另外加入以下依賴：

   <dependency>
       <groupId>org.slf4j</groupId>
       <artifactId>slf4j-log4j12</artifactId>
       <version>1.7.12</version>
   </dependency>

2. 將以下內容儲存為log4j.xml，檔案放在classpath的根目錄下。

   <?xml version="1.0" encoding="UTF-8"?>
   <!DOCTYPE log4j:configuration SYSTEM "log4j.dtd">
   <log4j:configuration xmlns:log4j="http://jakarta.apache.org/log4j/">
       <appender name="console" class="org.apache.log4j.ConsoleAppender">
           <param name="Target" value="System.out" />
           <layout class="org.apache.log4j.PatternLayout">
               <param name="ConversionPattern" value="%d %-5p [%t] %c{1} - %m%n" />
           </layout>
       </appender>
       <appender name="logfile" class="org.apache.log4j.DailyRollingFileAppender">
           <param name="File" value="log/sdk.log" />
           <layout class="org.apache.log4j.PatternLayout">
               <param name="ConversionPattern" value="%d %p [%c] - %m%n" />
           </layout>
       </appender>
       <logger name="com.aliyun.opensearch">
           <level value="debug" />
       </logger>
       <logger name="org.apache.thrift">
           <level value="error" />
       </logger>
       <root>
           <level value="info" />
           <appender-ref ref="console" />
           <appender-ref ref="logfile" />
       </root>
   </log4j:configuration>